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                        变量
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                        运算符
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                        语句
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                        函数
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                        定时器
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                        DOM操作
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                        在HTML中使用JavaScript
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                        JavaScript控制样式和属性
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                        <h1 id="string">String</h1>
<h2 id="&#x65B9;&#x6CD5;">&#x65B9;&#x6CD5;</h2>
<h3 id="charat">charAt()</h3>
<p>&#x8FD4;&#x56DE;&#x5728;&#x6307;&#x5B9A;&#x4F4D;&#x7F6E;&#x7684;&#x5B57;&#x7B26;&#xFF0C;&#x4ECE;&#x96F6;&#x5F00;&#x59CB;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> str1 = <span class="hljs-string">&quot;This is a string!!!&quot;</span>;
<span class="hljs-keyword">var</span> str2 = str1.charAt(<span class="hljs-number">10</span>); <span class="hljs-comment">// s</span>
</code></pre>
<h3 id="charcodeat">charCodeAt()</h3>
<p>&#x8FD4;&#x56DE;&#x5728;&#x6307;&#x5B9A;&#x7684;&#x4F4D;&#x7F6E;&#x7684;&#x5B57;&#x7B26;&#x7684; Unicode &#x7F16;&#x7801;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> str1 = <span class="hljs-string">&quot;This is a string!!!&quot;</span>;
<span class="hljs-keyword">var</span> str2 = str1.charCodeAt(<span class="hljs-number">10</span>); <span class="hljs-comment">// 115</span>
</code></pre>
<h3 id="concat">concat()</h3>
<p>&#x8FDE;&#x63A5;&#x4E24;&#x4E2A;&#x6216;&#x66F4;&#x591A;&#x5B57;&#x7B26;&#x4E32;&#xFF0C;&#x5E76;&#x8FD4;&#x56DE;&#x65B0;&#x7684;&#x5B57;&#x7B26;&#x4E32;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> str1=<span class="hljs-string">&quot;Hello &quot;</span>;
<span class="hljs-keyword">var</span> str2=<span class="hljs-string">&quot;world!&quot;</span>;
<span class="hljs-keyword">var</span> str3=<span class="hljs-string">&quot; Have a nice day!&quot;</span>;
<span class="hljs-keyword">var</span> n = str1.concat(str2,str3);
<span class="hljs-comment">//Hello world! Have a nice day!</span>
</code></pre>
<h3 id="fromcharcode">fromCharCode()</h3>
<p>&#x5C06; Unicode &#x7F16;&#x7801;&#x8F6C;&#x4E3A;&#x5B57;&#x7B26;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> n = <span class="hljs-built_in">String</span>.fromCharCode(<span class="hljs-number">72</span>,<span class="hljs-number">69</span>,<span class="hljs-number">76</span>,<span class="hljs-number">76</span>,<span class="hljs-number">79</span>);
<span class="hljs-comment">//HELLO</span>
</code></pre>
<h3 id="indexof">indexOf</h3>
<blockquote>
<p>&#x8FD4;&#x56DE;&#x7684;&#x662F;&#x4E0B;&#x6807;
```javascript
var str = &quot;abcdefgabcdefg&quot;;
var str2 = &quot;efg&quot;;
var str3 = &quot;xyz&quot;;
console.log(str.indexOf(str2));  //4  &#x8FD4;&#x56DE;&#x67D0;&#x4E2A;&#x6307;&#x5B9A;&#x7684;&#x5B57;&#x7B26;&#x4E32;&#x503C;&#x5728;&#x5B57;&#x7B26;&#x4E32;&#x4E2D;&#x9996;&#x6B21;&#x51FA;&#x73B0;&#x7684;&#x4F4D;&#x7F6E;&#xFF0C;str[4]&#x5F00;&#x59CB;
console.log(str.indexOf(str3));  //-1  &#x4E0D;&#x5B58;&#x5728;
console.log(str.lastIndexOf(str2));  //11  &#x4ECE;&#x8D77;&#x59CB;&#x4F4D;&#x7F6E;&#xFF08;0&#xFF09;&#x5F00;&#x59CB;&#x8BA1;&#x7B97;&#x8FD4;&#x56DE;&#x5B57;&#x7B26;&#x4E32;&#x6700;&#x540E;&#x51FA;&#x73B0;&#x7684;&#x4F4D;&#x7F6E;&#xFF0C;str[11]&#x5F00;&#x59CB;</p>
</blockquote>
<pre><code>
`indexOf(a,b)`&#xFF1A;
&#x7B2C;&#x4E00;&#x4E2A;&#x53C2;&#x6570;&#x4E3A;&#x9700;&#x8981;&#x7D22;&#x5F15;&#x7684;&#x5B57;&#x7B26;&#x4E32;&#xFF0C;
&#x7B2C;&#x4E8C;&#x4E2A;&#x53C2;&#x6570;&#x4E3A;&#x89C4;&#x5B9A;&#x5728;&#x5B57;&#x7B26;&#x4E32;&#x4E2D;&#x5F00;&#x59CB;&#x68C0;&#x7D22;&#x7684;&#x4F4D;&#x7F6E;&#xFF0C;&#x5B83;&#x7684;&#x5408;&#x6CD5;&#x53D6;&#x503C;&#x662F; 0 &#x5230; string Object.length - 1&#x3002;&#x5982;&#x7701;&#x7565;&#x8BE5;&#x53C2;&#x6570;&#xFF0C;&#x5219;&#x5C06;&#x4ECE;&#x5B57;&#x7B26;&#x4E32;&#x7684;&#x9996;&#x5B57;&#x7B26;&#x5F00;&#x59CB;&#x68C0;&#x7D22;&#x3002;

```javascript
var str1 = &quot;sdfasfasfsafsadfsasdfasf&quot;;
var str2 = &quot;sa&quot;;
var str3 = &quot;fa&quot;;

function search(str1,str2){
    for(var j=0;j&lt;str1.length;++j){
        j = str1.indexOf(str2,j);
        if(j&gt;=0){
            console.log(j);
        }
        else{
            return;
        }
    }
}

search(str1,str2);
search(str1,str3);
</code></pre><h3 id="replace">replace()</h3>
<p>&#x5728;&#x5B57;&#x7B26;&#x4E32;&#x4E2D;&#x67E5;&#x627E;&#x5339;&#x914D;&#x7684;&#x5B50;&#x4E32;&#xFF0C; &#x5E76;&#x66FF;&#x6362;&#x4E0E;&#x6B63;&#x5219;&#x8868;&#x8FBE;&#x5F0F;&#x5339;&#x914D;&#x7684;&#x5B50;&#x4E32;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> str1 = <span class="hljs-string">&quot;This is a string!!!&quot;</span>;

<span class="hljs-keyword">var</span> str2 = str1.replace(<span class="hljs-string">&quot;string&quot;</span>,<span class="hljs-string">&quot;sss&quot;</span>);

<span class="hljs-built_in">console</span>.log(str2);<span class="hljs-comment">//This is a sss!!!</span>
</code></pre>
<h3 id="slice">slice()</h3>
<p>&#x63D0;&#x53D6;&#x5B57;&#x7B26;&#x4E32;&#x7684;&#x7247;&#x65AD;&#xFF0C;&#x5E76;&#x5728;&#x65B0;&#x7684;&#x5B57;&#x7B26;&#x4E32;&#x4E2D;&#x8FD4;&#x56DE;&#x88AB;&#x63D0;&#x53D6;&#x7684;&#x90E8;&#x5206;&#x3002;</p>
<p>slice(start, end) &#x65B9;&#x6CD5;&#x53EF;&#x63D0;&#x53D6;&#x5B57;&#x7B26;&#x4E32;&#x7684;&#x67D0;&#x4E2A;&#x90E8;&#x5206;&#xFF0C;&#x5E76;&#x4EE5;&#x65B0;&#x7684;&#x5B57;&#x7B26;&#x4E32;&#x8FD4;&#x56DE;&#x88AB;&#x63D0;&#x53D6;&#x7684;&#x90E8;&#x5206;&#x3002;
&#x4F7F;&#x7528; <strong>start&#xFF08;&#x5305;&#x542B;&#xFF09;</strong> &#x548C; <strong>end&#xFF08;&#x4E0D;&#x5305;&#x542B;&#xFF09;</strong> &#x53C2;&#x6570;&#x6765;&#x6307;&#x5B9A;&#x5B57;&#x7B26;&#x4E32;&#x63D0;&#x53D6;&#x7684;&#x90E8;&#x5206;&#x3002;
&#x5B57;&#x7B26;&#x4E32;&#x4E2D;&#x7B2C;&#x4E00;&#x4E2A;&#x5B57;&#x7B26;&#x4F4D;&#x7F6E;&#x4E3A; 0, &#x7B2C;&#x4E8C;&#x4E2A;&#x5B57;&#x7B26;&#x4F4D;&#x7F6E;&#x4E3A; 1, &#x4EE5;&#x6B64;&#x7C7B;&#x63A8;&#x3002;</p>
<p><strong>&#x63D0;&#x793A;</strong>&#xFF1A; &#x5982;&#x679C;&#x662F;&#x8D1F;&#x6570;&#xFF0C;&#x5219;&#x8BE5;&#x53C2;&#x6570;&#x89C4;&#x5B9A;&#x7684;&#x662F;&#x4ECE;&#x5B57;&#x7B26;&#x4E32;&#x7684;&#x5C3E;&#x90E8;&#x5F00;&#x59CB;&#x7B97;&#x8D77;&#x7684;&#x4F4D;&#x7F6E;&#x3002;
&#x4E5F;&#x5C31;&#x662F;&#x8BF4;&#xFF0C;-1 &#x6307;&#x5B57;&#x7B26;&#x4E32;&#x7684;&#x6700;&#x540E;&#x4E00;&#x4E2A;&#x5B57;&#x7B26;&#xFF0C;-2 &#x6307;&#x5012;&#x6570;&#x7B2C;&#x4E8C;&#x4E2A;&#x5B57;&#x7B26;&#xFF0C;&#x4EE5;&#x6B64;&#x7C7B;&#x63A8;&#x3002;</p>
<pre><code class="lang-javascript">
<span class="hljs-keyword">var</span> str=<span class="hljs-string">&quot;Hello world!&quot;</span>;
<span class="hljs-keyword">var</span> n=str.slice(<span class="hljs-number">1</span>,<span class="hljs-number">4</span>);
<span class="hljs-comment">//ell</span>

<span class="hljs-keyword">var</span> n=str.slice(-<span class="hljs-number">1</span>);
<span class="hljs-comment">//!  &#x63D0;&#x53D6;&#x6700;&#x540E;&#x4E00;&#x4E2A;&#x5B57;&#x7B26;</span>
</code></pre>
<h3 id="split">split</h3>
<p>&#x628A;&#x5B57;&#x7B26;&#x4E32;&#x5206;&#x5272;&#x4E3A;&#x5B57;&#x7B26;&#x4E32;&#x6570;&#x7EC4;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> digite = <span class="hljs-string">&quot;0123456789&quot;</span>;
<span class="hljs-keyword">var</span> a2 = digite.split(<span class="hljs-string">&quot;&quot;</span>,<span class="hljs-number">5</span>);
<span class="hljs-comment">//&#x524D;5&#x4E2A;&#x5B57;&#x7B26;&#x5206;&#x5272;&#x6210;&#x5355;&#x5B57;&#x7B26;&#x7684;&#x6570;&#x7EC4;</span>
<span class="hljs-built_in">console</span>.log(a2);
</code></pre>
<h3 id="substr">substr()</h3>
<p>&#x4ECE;&#x8D77;&#x59CB;&#x7D22;&#x5F15;&#x53F7;&#x63D0;&#x53D6;&#x5B57;&#x7B26;&#x4E32;&#x4E2D;&#x6307;&#x5B9A;&#x6570;&#x76EE;&#x7684;&#x5B57;&#x7B26;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> str=<span class="hljs-string">&quot;Hello world!&quot;</span>;
<span class="hljs-keyword">var</span> n=str.substr(<span class="hljs-number">2</span>,<span class="hljs-number">3</span>);
<span class="hljs-comment">// llo</span>
</code></pre>
<h3 id="substring">substring()</h3>
<p>&#x63D0;&#x53D6;&#x5B57;&#x7B26;&#x4E32;&#x4E2D;&#x4E24;&#x4E2A;&#x6307;&#x5B9A;&#x7684;&#x7D22;&#x5F15;&#x53F7;&#x4E4B;&#x95F4;&#x7684;&#x5B57;&#x7B26;&#x3002;</p>
<p>substring() &#x65B9;&#x6CD5;&#x8FD4;&#x56DE;&#x7684;&#x5B50;&#x4E32;<strong>&#x5305;&#x62EC;&#x5F00;&#x59CB;&#x5904;</strong>&#x7684;&#x5B57;&#x7B26;&#xFF0C;&#x4F46;<strong>&#x4E0D;&#x5305;&#x62EC;&#x7ED3;&#x675F;&#x5904;</strong>&#x7684;&#x5B57;&#x7B26;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> str=<span class="hljs-string">&quot;Hello world!&quot;</span>;
<span class="hljs-built_in">console</span>.log(str.substring(<span class="hljs-number">3</span>));
<span class="hljs-built_in">console</span>.log(str.substring(<span class="hljs-number">3</span>,<span class="hljs-number">7</span>));
</code></pre>
<h3 id="touppercase">toUpperCase()</h3>
<p>&#x628A;&#x5B57;&#x7B26;&#x4E32;&#x8F6C;&#x6362;&#x4E3A;&#x5927;&#x5199;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> str=<span class="hljs-string">&quot;Hello world!&quot;</span>;
<span class="hljs-built_in">console</span>.log(str.toUpperCase());
</code></pre>
<h3 id="tolowercase">toLowerCase()</h3>
<p>&#x628A;&#x5B57;&#x7B26;&#x4E32;&#x8F6C;&#x6362;&#x4E3A;&#x5C0F;&#x5199;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> str=<span class="hljs-string">&quot;Hello world!&quot;</span>;
<span class="hljs-built_in">console</span>.log(str.toLowerCase());
</code></pre>

                    
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